In general, printed circuit boards (PCBs) mounted in information/telecommunication devices such as waste mobile phones contain precious metals such as gold, silver, and palladium, as well as valuable metals such as copper, tin, and nickel. Although the contents of the precious metals to be recovered vary depending on the model and production year of mobile phones, it is known that the printed circuit boards of mobile phones contain about 240-400 g/T of gold, about 2000-3000 g/T of silver, about 10-100 g/T of palladium, about 5-15 wt % of copper, 0.1-0.2 wt % of nickel, and 0.3-0.7 wt % of tin. In addition, precious metals which are used as catalysts for purifying automotive exhaust gases include platinum, palladium and rhodium, which are distributed as fine particles on the surface of honeycomb-type carriers at specific ratios. When automobiles are scrapped, spent automotive catalysts containing platinum, palladium, rhodium, and the like are generated, and the contents of these precious metals slightly vary depending on the manufacturer, model and production year of automobiles, but are about 55-790 g/T.
Meanwhile, as information/telecommunication devices are rapidly developed and the replacement cycle of automobiles is shortened, the generation of industrial waste such as waste mobile phone PCBs and spent automotive catalysts is sharply increased, and the environmental pollution caused thereby becomes a social issue.
However, precious metals contained in waste such as waste mobile phone PCBs and spent automotive catalysts are important as raw materials for high-tech products and are also high priced and high value-added, and hence are too precious to dispose of as waste. Thus, recovering and recycling such precious metals contributes to the national economy and is required in terms of effective utilization of resources.
A method for recovering precious metals from industrial waste such as mobile phone PCBs and spent automotive catalysts is broadly divided into a pyrometallurgical method and a hydrometallurgical method.
Among them, the hydrometallurgical method is a method of recovering precious metals from waste mobile phone PCBs and spent automotive catalysts by direct leaching using aqua regia or hydrochloric acid solution. In this method, there are disadvantages in that a large amount of wastewater is generated and the residue after recovery of precious metals is difficult to dispose of. For this reason, the hydrometallurgical method involves much difficulty in recovering precious metals from waste mobile phone PCBs and spent automotive catalysts which have low precious metal contents. Thus, the hydrometallurgical method has not yet been commercialized.
Meanwhile, the pyrometallurgical method includes a method that employs a nonferrous metal smelting furnace, and a method that employs an exclusive furnace.
The method that employs the nonferrous metal smelting furnace is a method of concentrating, separating and recovering precious metals as a nonferrous metal phase from waste mobile phone PCBs by charging the waste mobile phone PCBs together with nonferrous concentrate or copper matte into the nonferrous metal smelting furnace and melting the charged waste mobile phone PCBs at high temperature. This method has advantages in that no wastewater is generated and the generated slag can be effectively recycled because it has little or no adverse effect on the environment. However, there is a disadvantage in that a long working time is required. In addition, this method cannot be applied to industrial waste such as spent automotive catalysts which contain a large amount of alumina (Al2O3) that increases the viscosity of slag.
The method that employs the exclusive furnace can be divided into two categories: one in which various fluxes for controlling slag composition, such as alumina (Al2O3), caustic lime (CaO), magnesia (MgO), iron oxide (FeO) or silica (SiO2), a reducing agent such as carbon, and metals for capturing precious metals, such as copper, iron, lead or nickel, are added to waste mobile phone PCBs and spent automotive catalysts, which are then melted at high temperature, thereby recovering precious metals; and the other in which various fluxes for controlling slag composition, such as alumina (Al2O3), caustic lime (CaO), magnesia (MgO), iron oxide (FeO) or silica (SiO2), and a reducing agent such as carbon, are added to waste mobile phone PCBs and spent automotive catalysts, which are then melted at high temperature, thereby recovering precious metals.
The method that employs the exclusive furnace has advantages in that no wastewater is generated and the generated slag can be effectively recycled because it has little or no adverse effect on the environment. However, this method has a disadvantage in that it requires metals for capturing precious metals, such as copper, nickel, iron or nickel, various fluxes for controlling slag composition, such as alumina (Al2O3), caustic lime (CaO), magnesia (MgO), iron oxide (FeO) or silica (SiO2), and the reducing agent carbon in large amounts, which increases production cost. In addition, the excusive furnace-based method that does not employ the metals for capturing precious metals, such as copper, iron, lead or nickel, has a disadvantage in that, because the amount of alloy phase obtained in the process is small, the alloy phase is difficult to separate from the slag phase, resulting in an increase in process time.
Accordingly, the present inventors have made extensive efforts to solve the above-described problems occurring in the prior art and, as a result, have found that, when small amounts of waste nonferrous slag and caustic lime are added to waste mobile phone PCBs and spent automotive catalysts, which are then melted at high temperature, precious metals such as gold, silver, platinum, palladium and rhodium contained, in the waste mobile phone PCBs and the spent automotive catalysts, can be captured and concentrated in metals such as iron, copper, tin and nickel, contained in the waste nonferrous slag and the waste mobile phone PCBs, and can be simultaneously recovered. Based on this finding, the present invention has been completed.